Allardyce had been linked with the job at Goodison Park soon after the sacking of Ronald Koeman, but he ruled himself out of the running earlier this month after suggesting an agreement could not be reached.

Watford boss Marco Silva emerged as Everton's top target in the aftermath of Allardyce's initial rebuttal, while Burnley's Sean Dyche and Shakhtar Donetsk head coach Paulo Fonseca were also linked.

However, the Hornets played hardball over Silva, while the Dyche rumours failed to come to fruition and Everton struggled with Unsworth at the helm.

After leaving Palace, the 63-year-old Allardyce stated that he would only consider an international job, but the Everton post has proved too good to turn down.

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The club have endured a dismal 2017-18 season so far, winning just four of their first 14 matches.

Allardyce comes in as the official successor to Koeman, who was dismissed on October 23 after just two victories in nine Premier League games, despite spending an estimated £142 million in pre-season.

Unsworth took over on a caretaker basis but failed to inspire much of an improvement, as Everton lost five of his eight matches at the helm.